The disclosure relates to an application system and a corresponding application method for applying a fluid (e.g. PVC: polyvinylchloride) to a component (e.g. a motor vehicle bodywork component).
In modern coating systems for coating motor vehicle bodywork components, the material to be applied (e.g. PVC) is conveyed from a material supply to an applicator which applies the fluid to the component. Arranged between the material supply and the applicator is a flow measuring cell which can be configured, for example, as a spindle-type measuring cell, and which generates a volume flow signal corresponding to the fluid flow conveyed from the material supply to the applicator. However, the relationship between the volume flow signal emitted by the flow measuring cell and the actual volume flow depends on the property of the fluid conveyed, which makes suitable calibration necessary. Previously, this calibration of the flow measuring cell has been done manually in that the fluid output by the applicator is delivered into a measuring beaker during the calibration, while the volume flow signal of the measuring cell is measured. From the known volume of the measuring beaker and the measurement values of the flow measuring cell, a measuring specification can then be derived in order to calculate the actually conveyed volume flow of the fluid from the output signal of the flow measuring cell.
A first disadvantage of this calibration method is that the calibration must be carried out by hand, which is error-prone and is associated with an additional effort. Furthermore, during operation, the material properties of the fluid may change due, for example, to a temperature change or a charge change. Such changes may make a renewed calibration necessary, although typically it may not take place. Such deficiencies associated with this calibration method may lead to a deviation between the target quantity and the actual quantity of the applied fluid.
Reference is also made, with regard to the prior art, to DE 10 2007 053 073 A1, DE 10 2006 021 623 A1, EP 2 185 293 B1 and EP 1 854 548 A1. These publications also disclose an application system with a flow measuring cell and an evaluating unit wherein the evaluating unit determines from the measurement signal of the flow measuring cell the quantity flow (volume flow or mass flow) that flows through the flow measuring cell according to a measuring specification. Furthermore, these publications disclose that the application system can be calibrated. However, it is not the measuring specification that is calibrated in the evaluating unit, but the relationship between the flow rate through the flow measuring cell and the pressure and flow conditions downstream behind the flow measuring cell directly at the applicator. In general, a relatively long hose is arranged between the flow measuring cell and the applicator, so that the pressure and flow conditions at the flow measuring cell typically do not reflect the exact pressure and flow conditions at the applicator, but vary, e.g. as a result of “breathing” movements of the hose. The measuring specification stored in the evaluating unit is not calibrated in this case, but remains unchanged. In the context of the calibration, only the relationship between the flow rate through the flow measuring cell and the pressure and flow conditions at the applicator that are of interest are calibrated. A change to the measuring behaviour of the flow measuring cell (for example, due to a change in the temperature or viscosity of the fluid) can therefore not be taken into account in the context of the calibration, which leads to measuring errors.